Verification of Precision Equipment Used for Soil Specimen Shape Determination

Date of Graduation

12-2022

Document Type

Thesis

Degree Name

Bachelor of Science in Civil Engineering

Degree Level

Undergraduate

Department

Civil Engineering

Advisor/Mentor

Coffman, Richard A.

Committee Member

Barry, Michelle L.

Abstract

The properties of soil ultimately govern every structure that is built on land. Specifically, the shear strength of soil determines the maximum amount of stress that can be applied to the ground surface above the soil to ensure that the soil below the surface does not fail. In the event of a shear failure, the soil beneath the surface deforms, thus causing any structure that were to exist on the corresponding ground surface to fail as well. Therefore, knowledge about the soil must be obtained before various structures, including buildings and roadways, can be constructed. Testing of soil under applied stresses must be performed on soil samples obtained from the site of the proposed structure to understand the soil behavior.

Typically, soil is extracted from the site, and triaxial tests are performed to simulate field conditions. During the triaxial tests, the soil deforms, and the ways in which it deforms demonstrate the behavior under various stress states. The research described herein allowed for the modification of a device that was previously developed at the University of Arkansas to measure the deformation of a soil sample during such testing. Compared to the previous device, the modified device will allow for a better understanding of the soil behavior as more points on the soil surface are examined. The additional points on the soil surface will allow for greater coverage of the deformed soil surface, thus demonstrating how more positions of the soil react to the applied stresses. Such stresses mimic the presence of a structure and overburden load; therefore, a device that provides a better understanding of soil behavior under stresses equates to a device that provides a better understanding of the ground atop which a structure may be built.

The modified device was successfully designed, and the technology used within the device was verified through testing in both air and silicone oil. The highest quality settings of a pinhole aperture camera, one of the components of the modified device, were determined through a series of iterations. A calibration of the camera was then performed through three trials and ultimately failed as the error was too high. Therefore, to use the modified device, an accurate camera calibration must be performed.

Keywords

shear stress; triaxial cell; printed circuit board

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